Etch rate control

ABSTRACT

A method of forming a cavity in the side of a substrate (e.g., a mold plate adapted to be assembled with one or more additional plates to define a mold for a hook or a stem on a hook component of a touch fastener) includes forming on the substrate a layer of photoresist material on the substrate having a pattern of etchant-passing and etchant-blocking regions and applying a chemical etchant to the substrate such that the etchant undercuts the etchant-blocking regions to form a single contiguous cavity on the plate in an area beneath said pattern of etchant-passing and etchant-blocking regions.

TECHNICAL FIELD

This invention relates to photochemical etching to form cavities on asubstrate.

BACKGROUND

Photochemical etching commonly involves placing a mask over an etchablesubstrate that has been coated with a layer of photoresist material andthen exposing the photoresist material. If negative photoresist is used,the exposed areas of the photoresist become cured and resistant tochemical etchant. Areas of the photoresist that are not exposed arewashed away using a solvent leaving a portion of the underlyingsubstrate uncovered and ready for etching. If positive photoresist isused, then exposed areas are weakened and are easily washed away.

Once the photoresist mask has been applied, chemical etchant is appliedto the substrate to create a cavity in the uncovered areas of thesubstrate. Often applications, such as the creation of microhook moldsfor hook fasteners, seek to create very small molds that have complexshapes. U.S. Pat. No. 5,900,350 describes a method for creatingmicrohook molds for hook fasteners and is fully incorporated herein byreference.

SUMMARY

In one aspect, the invention features a method of forming a cavity on asubstrate (e.g., a microhook mold plate, semiconductor die, optical lensplate, etc.) that includes forming on the substrate a layer ofphotoresist material that includes a pattern of etchant-passing andetchant-blocking regions. Chemical etchant is applied to the substratesuch that etchant passed through the etchant-passing regions undercutsthe etchant-blocking regions to form a single contiguous cavity on thesubstrate in the area beneath the pattern of etchant-passing andetchant-blocking regions.

In some configurations, forming the patterned layer of photoresistmaterial on the first mold plate includes applying photoresist materialto at least one side of the substrate, placing over the photoresistmaterial a mask having a shaded region adapted to partially blockexposure of photoresist material disposed beneath the shaded region, andexposing the photoresist material to light through the mask. If negativephotoresist material is used, the unexposed areas are removed to createthe layer of photoresist material having a pattern of etchant-passingand etchant-blocking regions. If positive photoresist material is used,exposed areas are removed to create the patterned layer. Theetchant-passing regions of the photoresist in some configurations mayinclude apertures bounded by etchant-blocking regions, and theetchant-blocking regions may include discrete, bounded areas ofphotoresist material surrounded by etchant-passing regions void ofphotoresist material. The pattern of the etchant-passing andetchant-blocking regions may be uniform to form a cavity having asubstantially uniform depth or may be non-uniform to form a cavityhaving a variable depth. In some configurations the pattern ofetchant-passing and etchant-blocking regions may be selected to form acavity that extends completely through the substrate when etchant isapplied.

In some configurations, the substrate may be a mold plate adapted to beassembled with one or more additional plates to define a mold for a hookor stem on a hook component of a touch fastener.

In another aspect, the invention features a method of forming a cavityon a substrate that includes applying a photoresist material to thesubstrate, placing over the photoresist material a mask that has ashaded region adapted to partially block exposure of photoresistmaterial disposed beneath the shaded region, exposing the photoresistmaterial to light through the mask, and applying a chemical etchant tothe plate such that a single contiguous cavity is formed on thesubstrate in the area corresponding to the shaded region of the mask.

In another aspect, the invention features a method of forming asheet-form product having an array of projections extending from a broadsurface that includes forming a cavity on a first mold plate by forminga layer of photoresist material that includes a pattern ofetchant-passing and etchant-blocking regions on at least one side of thefirst mold plate. Chemical etchant is applied to the plate such that theetchant undercuts the etchant-blocking regions to form a singlecontiguous cavity on the plate in an area beneath the pattern ofetchant-passing and etchant-blocking regions. The first mold plate isassembled with one or more additional plates to form a mold, the cavitycooperating with a surface of an adjacent plate to at least partiallydefine one of an array of mold cavities extending inward from a surfaceof the mold. Resin is applied to the surface of the mold and forcingsome of the resin into the mold cavities to form an array of projectionsextending integrally from a layer of resin formed on the mold surface.

In some configurations, the formation of the patterned layer ofphotoresist material on the first mold plate includes applyingphotoresist material to at least one side of the plate, placing over thephotoresist material a mask having a shaded region adapted to partiallyblock exposure of photoresist material disposed beneath the shadedregion, and exposing the photoresist material to light through the mask.If negative photoresist material is used, the unexposed areas areremoved to create the layer of photoresist material having a pattern ofetchant-passing and etchant-blocking regions. If positive photoresistmaterial is used, exposed areas are removed to create the patternedlayer. The etchant-passing regions of the photoresist in someconfigurations may include apertures bounded by etchant-blockingregions, and the etchant-blocking regions may include discrete, boundedareas of photoresist material surrounded by etchant-passing regions voidof photoresist material. The pattern of the etchant-passing andetchant-blocking regions may be uniform to form a cavity having asubstantially uniform depth or may be non-uniform to form a cavityhaving a variable depth.

In some configurations, the cavity formed on the first mold plate is inthe shape of a hook or a stem for use in a hook component of a touchfastener.

In another aspect, the invention features a method of forming a moldform for making a sheet-form product having an array of projectionsextending from a broad surface that includes applying a photoresistmaterial to at least one side of a first mold plate, placing over thephotoresist material a mask having a shaded region adapted to partiallyblock exposure of the photoresist material disposed beneath the shadedregion, and exposing the photoresist material to light through the mask.Chemical etchant is applied to the plate such that a single contiguouscavity is formed on the plate in the area corresponding to the shadedregion of the mask. The first mold plate is assembled with one or moreadditional mold plates to form a mold such that the cavity cooperateswith a surface of an adjacent plate to at least partially define one oran array of mold cavities extending inward from a surface of the mold.

In some configurations, the shaded region of the mask includes a patternof light-blocking regions and light-passing regions (e.g., aperturesbounded by light-blocking regions or discrete, bounded areas of maskmaterial surrounded by light-passing regions void of mask material)printed on a non-opaque sheet (e.g., Mylar® film) using ahigh-resolution plotter or printer. The shaded region of the mask mayinclude an area having a uniform exposure density such application ofthe chemical etchant to the plate results in a cavity having anapproximately uniform depth in an area corresponding to the shadedregion of the mask having a uniform exposure density. The shaded regionmay include an area having a non-uniform exposure density such thatapplication of the chemical etchant to the plate results in a cavityhaving a variable depth in the area corresponding to the shaded regionof the mask having a non-uniform exposure density. The mask may alsoinclude a second region adapted to completely block exposure of thephotoresist material disposed beneath the second region.

In some configurations, the etchable plate defines a perimeter havingsome cross-sectional shape (e.g., circular, rectangular, etc) and thecavities are etched along the perimeter of the plate. The cavity formedin the plate may have a hook shape such as one that includes a base anda tip and a cross-sectional area that tapers from the base of the cavityto the tip. The cavity may also have hook shape that includes a pedestalportion contiguous to a crook portion and at least one barb protrudingfrom either the pedestal portion or the crook portion. In otherconfigurations, the cavity may have a stem shape.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of a side view of a hook mold.

FIGS. 2-3 are cut away views of the hook mold shown in FIG. 1.

FIGS. 4-5 are diagrams of a hook component of a touch fastener.

FIG. 6 is a diagram of a process for making molded hook members.

FIGS. 7A-7C are diagrams of a molding roll for making molded hookmembers.

FIG. 8 is a diagram of a mask used to create a cavity for a hook mold.

FIGS. 9A-9D are a series of diagrams illustrating a process for creatinga cavity for a hook mold.

FIGS. 10A-10D are a series of diagrams illustrating a process forcreating a cavity having a gradually increasing depth on a substrate.

FIGS. 11A-11C are diagrams of masks used to create cavities for hookmolds.

FIGS. 12A and 13A are diagrams of masks used to create the hooks shownin FIGS. 12B and 13B respectively.

FIGS. 12B and 13B are diagrams showing the front view of a hook memberformed using a mold formed from the masks shown in FIGS. 12A and 13Arespectively.

FIGS. 14A-14C are diagrams of masks used to create cavities for hookmolds.

FIGS. 15A, 15C, 15E, 16A, and 17A are diagrams of masks used to createhooks and stems shown in FIGS. 15B, 15D, 15F, 16B and 17B respectively.

FIGS. 15B, 15D and 15F are diagrams showing the front view of a hookmember formed using a mold formed from the masks shown in FIGS. 15A, 15Cand 15E respectively.

FIG. 16B is a diagram showing a perspective view of the stem createdfrom the mask shown in FIG. 16A.

FIG. 17B is a diagram showing the top view of a stem created from themask shown in FIG. 17A.

FIG. 18A is a diagram of the mask used to create the stem shown in FIGS.18B- 18C.

FIGS. 18B and 18C are diagrams showing the side view and cross-sectionalview, respectively, of a stem formed using the mask shown in FIG. 18A.

FIG. 18D is a diagram of a stem-like hook formed from the stem shown inFIGS. 18B-18C.

FIG. 19 is a diagram of a mask used to create cavities for hook moldsthat include loop diverters.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, a mold cavity 10, which is used to form a hookon a hook component of a touch fastener, defines a pedestal portion 12and a crook portion 14 and has a height H. The pedestal portion 12 ofthe mold cavity 10 has a cross-section that has a width W1 at one edge16 of the cavity tapering out to width W2 in the center portion 18 andtapering back to width W1 at the other edge 20 of the cavity. Similarly,the crook portion 14 of the mold cavity has a cross-section that haswidth W1 at one edge 22 tapering out to width W2 in the center portion24 and tapering back to width W1 at the other edge of the cavity 26. Thethickened portion of the mold cavity, e.g., portions 18, 24,advantageously provides strength and resiliency to a hook formed frommold cavity 10.

Referring to FIGS. 4 and 5, a hook component 30 of a touch fastenerincludes a sheet form base 32 and multiple parallel rows of integrallymolded hook members 34. The molded hook members are formed from a moldcavity similar to the mold cavity shown in FIGS. 1 and 2, and,therefore, have a tapered cross-sectional widths ranging from W1 to W2.Ripstop bumps (not shown), i.e., known raised local regions of the basein spaces between rows of integrally molded hook members, may beemployed either aligned with the hook members or offset from the hookmembers, depending upon the intended application.

In one implementation, there are approximately 24 hook members perlineal inch (9.44 hook members per lineal centimeter). The hook membersare preferably spaced apart laterally (i.e., in the cross-machinedirection) a distance 36 of about 0.008 inches (0.203 millimeters), andthe pedestals 12 have a maximum thickness, W2, of about 0.006 inches(0.152 millimeters). This yields a density in the cross-machinedirection of approximately 71 hook members per inch (27.95 members perlinear centimeter). Hence, there are on the order of 1700 hook membersper square inch (263.5 members per square centimeter) in thisimplementation.

As shown in FIG. 6, a method for making such molded hook members entailsextruding molten resin 40 into the nip formed between a cooled moldingroll 42 and a pressure-applying roll 44. The cooled molding roll hasmold cavities 10 about its periphery that are configured to produce hookmembers. A backing sheet 46, such as a woven or non-woven fabric, may besupplied from a backing sheet roll 48 to the nip. This backing sheet maycontain loops adapted to engage the hook members. The resulting fastenerelement will then include hook members bound to the backing sheet inwhat may be termed an in situ laminating process. This process isdescribed and illustrated in more detail in U.S. Pat. No. 5,900,350.

Referring to FIGS. 7A-7C, the molding roll 42 includes a series of toolrings 50 mounted on a cooled central barrel 52. The rings are pressedtogether axially to form a cylindrical surface. Mold cavities 10 aredisposed along the periphery of a pair of adjacent tool rings, e.g.,tool rings 50 a, 50 b. Spacer rings 54 are disposed between pairs ofadjacent tool rings to provide the desired spacing between rows of moldcavities (e.g., dimension 36 shown in FIG. 5). The mold cavities, alongwith any bumps or other formations in the tool ring, are provided in apredetermined relationship to provide hook members on the base in adesired relationship, as the particular application requires. While inthis implementation all of the mold cavities 10 formed by a mating pairof mold plates are identical, other implementations may use a variety ofmold cavities formed by a mating pair of mold plates.

The mold cavities 10 are formed along the periphery of the tool rings bya chemical etch process. In one implementation, a tool ring formed of17-7 PH stainless steel or other material susceptible to chemicaletchant is coated with a layer of negative photoresist material. A mask,shown in FIG. 8, is placed over the photoresist and then exposed.Unexposed areas of the photoresist (i.e., the areas beneath theblacked-out portion of the mask) are removed using a solvent, e.g., anaqueous alkaline solution, which leaves the underlying substrateuncovered and ready for etching. The tool ring is then placed on amachine and sprayed with a strong acid, which removes exposed areas ofthe tool ring.

As shown in FIGS. 9A-9D, the depth of the etch is controlled by theexposure density of shaded area of the mask. In particular, whennegative photoresist is employed, a deeper etch will result in areasbeneath the mask that have a low exposure density (e.g., the completelyblacked out area 61 of the mask 60) than in areas beneath the mask thathave a higher exposure density (e.g., the shaded area 62 of the mask60). Referring to FIG. 9A, an etchable tool ring 50 is coated with anegative photoresist material 64 and a patterned mask 60 is placed overthe coated substrate. The photoresist material is exposed to light 65causing the exposed areas to become cured and resistant to chemicaletchant. Non-exposed areas of the photoresist (i.e., the areas beneaththe blacked-out portions of the mask) are washed away and chemicaletchant is sprayed on the tool ring. In areas where there is arelatively large gap between exposed areas of the plate, e.g., thecompletely blocked-out area 61 of mask 60 shown in FIG. 8, the etchantetches a relatively deep cavity 66 having a depth of ½ W2. In areaswhere the exposed areas of the plate are close together, e.g., theshaded area 62 of mask 60, the etchant etches a series of shallowcavities 67 that completely undercut adjacent areas of cured photoresistto form a single cavity 68 a, 68 b beneath the shaded areas of the maskhaving a depth of ½ W1.

Similarly, as shown in FIGS. 10A-10D, a cavity 70 having a depth thatgradually tapers from a relatively shallow depth at one end 71 a to arelatively deeper depth at the other end 71 b of the cavity is formedusing a mask 69 having a series of light-blocking regions of increasinglength. In particular, as shown in FIG. 10A, an etchable substrate 72 iscoated with negative photoresist material 64 and a mask 69 is applied tothe top of the photoresist material 64. The mask 69 has a pattern inwhich the distance between light-passing regions 73 a-73 e graduallyincreases from one end of the pattern to the other (i.e., D1<D2<D3<D4).The photoresist material is exposed to light 65 through the mask and thenon-exposed areas (i.e., the areas beneath the light-blocking regions ofthe mask) are removed leaving a similar pattern of etchant-passingregions 74 a-74 d and etchant-blocking regions 75 a-75 e on thesubstrate. Chemical etchant is then applied to the prepared substrate tocreate a series of gradually deeper etches corresponding to thegradually increasing distance between etch-blocking regions. The etchantundercuts the interior etchant-blocking regions 75 b-75 d to create acontiguous cavity having a tapered depth.

In one implementation, the shaded mask, such as mask 60 shown in FIG. 8,is formed by plotting the mask pattern on a sheet of non-opaque material(e.g., glass plate or a plastic film such as Mylar® manufactured by E.I.du Pont de Nemours and Company headquartered in Wilmington, Del.) usinga high-resolution plotter (e.g., 10,000 dpi). Other implementations mayuse other known techniques for creating photoresist masks, such asprinting photoresist having the selected pattern directly on a substrateor printing masks using high-resolution printers. As shown in FIGS.11A-11C, a mask may use a variety of patterns to control the depth ofthe etch, including dots, apertures, lines, crosshatch or combinationthereof.

The use of a shaded photoresist mask in a photo-etching process providesa cost effective technique for creating hooks with a wide variety ofshapes and features. For example, as shown in FIGS. 12A-12B, a hook 80having a relatively wide pedestal portion 82 and a narrow crook portion82 is formed using a mask 86 having a shaded crook portion and acompletely blocked-out pedestal portion 89.

Similarly, as shown in FIGS. 13A-13B, a hook 90 that gradually tapersfrom a wide base 92 to a narrow crook 94 is formed using a mask 96 thatis densely shaded at the base 98 and gradually becomes less denselyshaded along the length of the mask. A tapered hook that comes to arelatively thin crook, such as that shown in FIG. 13B, is effective forgrabbing loops. However, if the hook is too thin in the crook region,the hook is susceptible to deformation or breakage during use. A mask,such as mask 100 shown in FIG. 14A, may be used to maintain a taperedtip 102 for effective grabbing of hooks, while at the same time having athickened portion 104 to add strength and resiliency to the crook regionof the hook.

Because the crook portion of a hook is often substantially narrower thanits base, a mold cavity etched with a uniformly shaded mask (e.g., acompletely blacked-out mask) will often be shallower at the tip than atthe base, thus creating a hook that is narrower at its tip than at itsbase. This etching difference can be compensated using a mask, such asmask 104 shown in FIG. 14B, that completely masks the tip 108 of themold cavity and partially masks the base 110.

Referring to FIG. 14C, a hook may be formed that has a narrow centralregion by using a mask 112 that partially masks the central region 114of the mold cavity and completely masks the base 116 and tip 118 of themold cavity. This narrow central region can be beneficial for active andprolonged engagement with a loop.

As shown in FIGS. 15A-15F, barbs 122 or other grabbing features areincorporated in hooks 124, 126, 128 using a mask 130, 132, 134 that hasblocked-out or very densely shaded areas in locations 136 where a barbis desired. A barb located at or near the end of a hook, such as hook126 shown in FIG. 15D, is also beneficial for prolonged engagement witha loop, and may result in an increase in the strength properties of theclosure.

Shaded masks may be used to fabricate mold plates for a hook componentof a touch fastener that employs stems and stem-like hooks described inU.S. application Ser. No. 10/455,240 filed Jun. 4, 2003, entitled “Hookand Loop Fastener” to Mark A. Clarner, George A. Provost, and William L.Huber, which is fully incorporated herein by reference. For example, asshown in FIGS. 16A-16B, a pronged stem-like hook 140 is formed using amask 142 that has alternating bands of relatively densely-shaded areas146 and relatively lightly-shaded areas 144. Similarly, as shown inFIGS. 17A-17B, a quadralobal stem 150 is formed using a mask 152 thathas a relatively densely shaded band centered between two relativelylightly shaded bands 156. A mask with a densely-shaded area thatgradually decreases in density towards the sides, such as mask 166,shown in FIG. 18A, could be used to create a cylindrical stem, 168,shown in FIGS. 18B-18C. Stem 168 could then be post-formed into astem-like hook such as hook 170 shown in FIG. 18D.

As shown in FIG. 19, a mask 160 includes a shaded region for a hookelement 162 and two densely shaded regions 164 for a pair of hookdiverter elements. Hook diverter elements are ridges or bumps areemployed in some application to direct loops around hook elements. Inthis example, the hook diverter portion of the mask 164 is denselyshaded to create a deeper etch, which results in a larger, moreeffective loop diverter.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, in each of the above examples negative photoresist is used.While negative photoresist is currently preferred from a costperspective, positive photoresist may also be used. When positivephotoresist is used, areas that are exposed are weakened and becomesoluble and thus easily removed and the remaining portion of thephotoresist (i.e., the area covered by a mask) remains on the plate.Therefore, masks adapted for use with positive photoresist will be thenegative image of a mask adapted for use with negative photoresist.

As explained in detail in U.S. Pat. No. 5,900,350, hooks formed frommold rolls, such as roll 42 shown in FIG. 6, are often deformed duringthe molding process such that the resulting hook is not identical to themold form. As a result, the mold cavities may be formed using a maskthat compensates for the deformation that occurs during the moldingprocess to produce a hook of the desired form. Other implementations mayemploy a mask having shaded regions to control the depth of theresulting mold cavity as described in this disclosure and also use thedeformation compensation techniques described in U.S. Pat. No.5,900,350.

Additionally, the mold cavities need not be formed on a tool ringadapted to produce hook fasteners by passing molten resin into a nipformed between a cooled molding roll and a pressure-applying roll asillustrated in FIG. 6, but may be formed on plates adapted to producehook fasteners using other techniques. For example, a series of moldcavities may be formed on periphery of etchable plates having straightedges, which when assembled together to form a generally flat moldassembly having a series of mold cavities. Hook fasteners may then beproduced by injecting or pouring molten resin onto the flat moldassembly or by stamping a sheet of molten resin with the flat moldassembly.

Moreover, the techniques described for fabricating a microhook moldcavity may be extended to a wide variety of other photochemical etchingapplications in which a cavity is etched on a substrate, such as forminga lens from a glass substrate, fabricating a tapered disk drive datahead from a metallic substrate, or fabricating an integrated circuitfrom a semiconductor substrate.

Accordingly, other embodiments are within the scope of the followingclaims.

1. A method of forming a sheet-form product having an array ofprojections extending from a broad surface thereof, the methodcomprising: forming a cavity on a first mold plate, including: forming alayer of photoresist material on at least one side of the first moldplate, the layer of photoresist material comprising a pattern ofetchant-passing and etchant-blocking regions; and applying a chemicaletchant to the plate such that the etchant undercuts theetchant-blocking regions to form a single contiguous cavity on the platein an area beneath said pattern of etchant-passing and etchant-blockingregions; assembling the first mold plate with one or more additionalplates to form a mold, the cavity cooperating with a surface of anadjacent plate to at least partially define one of an array of moldcavities extending inward from a surface of the mold; and applying resinto the surface of the mold and forcing some of the resin into the moldcavities to form an array of projections extending integrally from alayer of resin formed on the mold surface.
 2. The method of claim 1wherein forming a layer of photoresist material comprises: applyingphotoresist material to at least one side of the first mold plate;placing a mask over the photoresist material, the mask comprising ashaded region adapted to partially block exposure of photoresistmaterial disposed beneath the shaded region; and exposing thephotoresist material to light through the mask.
 3. The method of claim 1wherein the etchant-passing regions comprise apertures bounded by saidetchant-blocking regions.
 4. The method of claim 1 wherein theetchant-blocking regions comprise discrete, bounded areas of photoresistmaterial surrounded by etchant-passing regions void of photoresistmaterial.
 5. The method of claim 2 wherein the photoresist materialcomprises negative photoresist material and the exposure to light curesthe photoresist material onto the plate, such that the photoresistmaterial not exposed to the light is removed.
 6. The method of claim 2wherein the photoresist material comprises positive photoresist materialand the exposure to light weakens the positive photoresist material suchthe photoresist material exposed to the light is removed.
 7. The methodof claim 1 wherein the pattern of etchant-passing and etchant-blockingregions is uniform.
 8. The method of claim 7 wherein the cavity formedon the plate has an approximately uniform depth in the area beneath saidpattern.
 9. The method claim 1 wherein the pattern of etchant-passingand etchant-blocking regions is non-uniform.
 10. The method of claim 9wherein the cavity formed on the plate has a variable depth in the areabeneath said pattern.
 11. The method of claim 1 wherein the cavity has ahook shape.
 12. The method of claim 1 wherein the cavity has a stemshape.
 13. A method of forming a mold for forming a sheet-form producthaving an array of projections extending from a broad surface thereof,the method comprising: applying a photoresist material to at least oneside of a first mold plate; placing a mask over the photoresistmaterial, the mask comprising a shaded region adapted to partially blockexposure of photoresist material disposed beneath the shaded region;exposing the photoresist material to light through the mask; andapplying a chemical etchant to the plate such that a single contiguouscavity is formed on the plate in the area corresponding to the shadedregion of the mask; assembling the first mold plate with one or moreadditional plates to form a mold, the cavity cooperating with a surfaceof an adjacent plate to at least partially define one or an array ofmold cavities extending inward from a surface of the mold.
 14. Themethod of claim 13 wherein the photoresist material comprises negativephotoresist material and the exposure to light cures the photoresistmaterial onto the plate, such that the photoresist material not exposedto the light is removed.
 15. The method of claim 13 wherein thephotoresist material comprises positive photoresist material and theexposure to light degrades the positive photoresist material such thephotoresist material exposed to the light is removed.
 16. The method ofclaim 13 wherein the shaded region of the mask comprises a pattern oflight-blocking regions and light-passing regions.
 17. The method ofclaim 16 wherein the light-passing regions comprise apertures bounded bylight-blocking regions.
 18. The method of claim 16 wherein thelight-blocking regions comprise discrete, bounded areas of mask materialsurrounded by light-passing regions void of mask material.
 19. Themethod of claim 13 wherein the shaded region of the mask comprises apattern of lines.
 20. The method of claim 13 further comprising formingthe mask using a plotter.
 21. The method of claim 13 wherein the shadedregion of the mask comprises an area having a uniform exposure densitysuch that application of the chemical etchant to the plate results in acavity having an approximately uniform depth in the area correspondingto the shaded region of the mask having a uniform exposure density. 22.The method of claim 13 wherein the shaded region of the mask comprisesan area having a non-uniform exposure density such that application ofthe chemical etchant to the plate results in a cavity having a variabledepth in the area corresponding to the shaded region of the mask havinga non-uniform exposure density.
 23. The method of claim 13 wherein themask further comprises a second region adapted to completely blockexposure of the photoresist material disposed beneath the second region.24. The method of claim 13 wherein the cavity has a hook shape includinga base and a tip and a cross-sectional area that tapers from the base ofthe cavity to the tip.
 25. The method of claim 13 wherein the cavity hasa hook shape that includes a pedestal portion and a crook portion whichare contiguous and further including at least one barb protruding fromeither the pedestal portion or the crook portion.
 26. The method ofclaim 13 wherein the first mold plate defines a perimeter, and the moldcavities are disposed along the perimeter of the plate.
 27. The methodof claim 13 wherein the etchable plate is ring-shaped.
 28. A method offorming a cavity on a substrate the method comprising: forming a layerof photoresist material on the substrate, the layer of photoresistmaterial comprising a pattern of etchant-passing and etchant-blockingregions selected to form a single contiguous cavity in the substrate inthe area beneath said pattern when a chemical etchant is applied; andapplying a chemical etchant to the substrate such that the etchantundercuts the etchant-blocking regions to form a single contiguouscavity on the plate in an area beneath said pattern of etchant-passingand etchant-blocking regions.
 29. The method of claim 28 wherein forminga layer of photoresist material comprises: applying photoresist materialto the substrate; placing a mask over the photoresist material, the maskcomprising a shaded region adapted to partially block exposure ofphotoresist material disposed beneath the shaded region; and exposingthe photoresist material to light through the mask.
 30. The method ofclaim 28 wherein the substrate is a mold plate adapted to be assembledwith one or more additional plates to define a mold for a hook or- stemon a hook component of a touch fastener.
 31. The method of claim 28wherein the etchant-passing regions comprise apertures bounded by saidetchant-blocking regions.
 32. The method of claim 28 wherein theetchant-blocking regions comprise discrete, bounded areas of photoresistmaterial surrounded by etchant-passing regions void of photoresistmaterial.
 33. The method of claim 29 wherein the photoresist materialcomprises negative photoresist material.
 34. The method of claim 29wherein the photoresist material comprises positive photoresistmaterial.
 35. The method of claim 28 wherein the pattern ofetchant-passing and etchant-blocking regions is uniform.
 36. The methodof claim 35 wherein the cavity formed on the plate has an approximatelyuniform depth in the area beneath said pattern.
 37. The method claim 28wherein the pattern of etchant-passing and etchant-blocking regions isnon-uniform.
 38. The method of claim 37 wherein the cavity formed on theplate has a variable depth in the area beneath said pattern.
 39. Themethod of claim 28 wherein at least a portion of the cavity penetratesthrough the substrate.